The display of a three dimensional world to a viewer requires considerable computation power, and it is typically costly to develop the necessary highly detailed models required for doing so. In order to simplify the problem, a portion of the world that is in the distance may be represented in only two dimensions as a video displayed on a surface, e.g., a screen. By video it is meant the common usage of the term, such as the placing or projecting of predefined images on the surface, e.g., the electronic version of filmed moving pictures. Thus, such a world is essentially truncated in length to the screen on which the video is displayed. A great reduction in computation power and cost can be achieved by such an arrangement.
In U.S. patent application Ser. No. (case Carraro-Ensor 2-7) it was recognized that a limitation of such a world occurs when an object within the field represented by the video undergoes a trajectory that takes it to a location in the world that is not represented by the video but instead is a location in the foreground which is represented by computer graphics, namely, any portion of the object that is no longer on the video screen, disappears. Therefore, when an object within the field represented by the video undergoes a trajectory that takes it, or a portion thereof, to a location in the world that is not represented by the video but instead is a location in the foreground which is represented by computer graphics, such an object or portion is made to continue to be visible to the user and is represented at the foreground location using computer graphic techniques, rather than video. Thus, the video object "pops" out of the video and becomes visible, e.g., in front of, or to the side of, the video screen, rather than becoming invisible because it is no longer on the video screen.